A novel xerographic system architecture and methodology affords the opportunity to achieve smoother halftones in light critical areas while alleviating ink-limit stress through use of a tri-level process and one or more hypochromatic light colorants.
Photographic quality inkjet printers have, for a number of years, taken advantage of light colorant strength ink capability to significantly drive down image noise levels for highlight/midtone areas, particularly for fleshtone and blue sky regions, for example. However, the ability to achieve a similar advantage with current xerographic platforms is difficult due to the difficulties associated with designing halftone screens for more than 4 distinct colors on xerographic systems with color misregistration issues, and other xerographic process limitations, such as ink limits and prohibitive cost of consumables.
Some commercial products achieve printing using light hypochromatic colorants. However, such products require interlaced halftone screens that require extremely tight registration requirements of about 10 microns to enable dot-on-dot halftoning. This multipass marking engine struggles to achieve this level of accuracy and is susceptible to objectionable registration induced color shifts. Many other architectures, particularly single pass architectures, will also struggle without increased cost and/or complexity.
Typically, registration sensitivity for conventional marking engines is reduced through the use of rotated screens. However, this approach becomes less effective and vulnerable to moiré as the number of colorants and required screens increases, and this may defeat benefits of using hypochromatic colorants.